Conventional hammers typically include a head and a handle. During use, a strike surface disposed on the head of the hammer is configured to strike against an object, such as a nail. Placing the nail with fewer strikes, with fewer failures, less concussive vibration and less energy output from the user are some objectives of hammer makers.
The common use of nail-starters on hammers has partially overcome the problem of requiring two hands to start a nail and hence removed some of the risk of injury to fingers. Many available hammers have a nail-starter located on the top front portion of the head. A lateral groove, configured to a length of at least 3.5 cm (1⅜ in.) from bell face to partial nail starter face, with a recessed magnet that retains the nail shank. The nail head rests in a generally rounded opening with a gradually sloping partial strike face that extends upward, supporting only a portion of the common nail head. This partial strike face is constructed so as to apply a limited amount of force to the nail head before the nail slides out from the nail head opening and loses contact. Hence the nail shaft is implanted to a shallow depth within the work piece surface. It is an acceptable, but not a consistently reliable means of nail starting and this is perhaps why it often referred to as an optional hammer feature, (eg., U.S. Pat. No. 8,047,099 B2) which states: The nail starter arrangement that includes the groove 64, magnet 67, and the surface 69 are optional.
There are a number of prior art nailing tools that have approached the problem of placing a nail that has been retained by the hammer. One technique, used in U.S. Pat. No. 5,894,764, confines and therefore restricts the nail head movement with both a vertical and horizontal wall and is only capable of a placing the nail to limited depth in a work piece. This typifies the fixed nail head nail starter method, whereby any nail depth placement in the work piece more than a minimal amount can result in a bent head, bent nail shaft or misdirected nail shaft. There are a number of limited nail starter methods and tools available, including commonly available nail-starters disposed on typical nailing hammers. Some relevant prior art that employ typical and alternate methods are:    Pat. US 20110314971 A1Which incorporates a nail magazine and mechanism to deliver nails.    U.S. Pat. No. 4,273,172 AWhich offers a limited force strike with a restricted nail head.    U.S. Pat. No. 2,597,876 AWhich offers a fixed head holder and limited depth placement of the shaft.    U.S. Pat. No. 4,193,433 AWhich retains the nail head with a hook beneath claw and offers limited nail shaft depth.    U.S. Pat. No. 6,301,996 B1Which offers a limited depth with a multiple angle restriction upon the nail head.
These methods either confine and restrict the nail head or deliver a limited glancing strike. If the nail head is restricted the friction and forces that act upon the nail head cause it to be misdirected or cause the nail shaft to bend. The limited glancing strike of the typical partial strike face nail-starters can only drive the nail shaft in to a limited depth. These nail-starters are configured with only a limited amount of weight directly behind the partial nail head strike face.
When using the typical integrally formed nail-starter, the second strike, after initially planting the nail, is critical. The shallow depth of the initial nail start makes the successive strike, usually the most forceful, also the most likely to produce failure. This second blow requires more skill and accuracy to ensure an acceptable continuation of the nail placement, sometimes resulting in bent nail shafts or nails completely ejected from the work piece. If the second strike is successful it is commonly followed by a number of additional strikes, each one having a level of difficulty and having the possibility of bending or misdirecting the nail. The total number of strikes required is usually between 4 and 6, depending on, among other factors, nail size and desired depth.
Magnetic face specialty tools, usually referred to as tack hammers, roof paper hammers or upholstering hammers, have existed for more than one hundred years. These tools require specialized fasteners that typically have one or more of the following attributes; sharper points, shorter shafts, reinforced heads and/or oversized heads. Some prior art examples of tack hammers are as follows:    Magnetic tack-hammer U.S. Pat. No. 840,441 A    Magnetic tack-hammer U.S. Pat. No. 710,615 A    Tack hammer U.S. Pat. No. 2,433,223 A    Nail or tack holding attachment for hammers U.S. Pat. No. 469,710 A    Magnetic roofing hammer U.S. Pat. No. 20030140734 A1    Coil Nailer U.S. Pat. No. 20110049215 A1
Nail length is also an issue with typical nail starters. In order to function the nail length must be greater than the distance from the nail-starter strike face to the hammer strike face. Typically nails shorter than 3.8 cm (1½ in.) cannot utilize the common bell head nail starter.
Another problem with commonly used hammers is that they require a multitude of strikes in order to place the nail in a surface to a predetermined depth. Typically, said depth is more than 80 percent of the nail shaft length. Transporting the hammer weight in an arcing motion for a multitude of strikes in order to achieve this depth causes muscle stress and fatigue in the user.
An additional problem with repeated hammer face to nail head strikes is twist and vibration. Common hammer handles have a tendency to transfer torque (the twisting across the longitudinal axis of the handle) and kinetic energy caused by metal impacting metal to the user when a nail head is struck. This problem is compounded by the fact that the most control is required at the moment of impact between hammer face and nail head. The user must grip the handle the tightest at that time. This is when the most kinetic energy and twist occur within the handle, creating faster fatigue and adding more muscle stress to the user.
The following is a list of relevant prior art:    U.S. Pat. No. 20120036965 A1    U.S. Pat. No. 7,404,346 B2    U.S. Pat. No. 4,667,747 A    U.S. Pat. No. 3,788,373 A    EP Pat. No. 2517837 A2
This embodiment of the present invention overcomes these problems by combining the nail-start strike and first full strike into one continuous action. Among other factors, it is the freedom of movement between nail head and striking surface afforded by the present invention which thereby allows the nail to be struck with full force. The nail shaft and nail head remain in their original uniform configuration and transverse directly into the work piece. Hence the nail is placed more consistently, with more reliability and with fewer strikes. Since there are fewer strikes required, and commonly only two metal on metal strikes, there is less energy output from the user and less concussive vibration.
This embodiment of the present invention is also configured with the preferred distance of 15 mm (⅝ in.) from the front edge, (horizontal cylinder segment strike-face), to the nail-starter strike face. Therefore, said embodiment provides a means for placing any nails minimally longer than 15 mm (⅝ in.). The 15 mm horizontal cylinder segment also provides a means to place nails in one strike to a depth whereby 15 mm of the nail is all that remains above the work piece surface.
These and other advantages of the present invention will be readily apparent to those of ordinary skill in the art upon a reading of the following detailed description of presently preferred, but nonetheless illustrative, embodiments of the present invention when taken in conjunction with the accompanying drawings. In this respect, before explaining the current embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of descriptions and should not be regarded as limiting.